An electric vehicle widely used in recent years is not provided with an engine (internal combustion engine) for outputting a drive force of running a vehicle and hence does not utilize the waste heat of the engine as a heat source in heating the inside of a vehicle compartment. Hence, an air conditioning device for heating the inside of the vehicle compartment by using a high temperature and high pressure refrigerant discharged from an electric compressor of a heat pump cycle (vapor compression type refrigeration cycle) is known as a vehicular air conditioning device applied to the electric vehicle (see, for example, Patent Documents 1, 2)
In this kind of air conditioning device, when the heat load of the heat pump cycle is increased and the amount of electricity consumed by the electric compressor is increased, as in the heating operation when an outside air temperature is low, the amount of electricity that the electric motor for running the vehicle can consume is decreased. Therefore, in this case, a travel distance of the vehicle will be made shorter.
Hence, in the patent document 2, a so-called gas injection cycle (economized refrigeration cycle) is employed as a heat pump cycle to thereby improve the coefficient of performance (COP) of the cycle, whereby the power consumption of the electric compressor is reduced.
For example, the heat pump cycle of the patent document 2 is provided with: a heat radiator for making a refrigerant, which is discharged from a discharge port of the electric compressor and has high temperature and high pressure, radiate heat; a high-pressure side pressure reducing device and a low-pressure side pressure reducing device for reducing the pressure of the refrigerant flowing out of the heat radiator to thereby expand the refrigerant in two steps; a gas-liquid separator for separating gas and liquid of an intermediate pressure refrigerant having pressure reduced by the high-pressure side pressure reducing device; and an evaporator for evaporating a low pressure refrigerant having the pressure reduced by the low-pressure side pressure reducing device to thereby make the low pressure refrigerant perform a heat absorption action.
A gas-phase refrigerant separated by the gas-liquid separator is mixed with the refrigerant in a compression process which is discharged from an intermediate pressure port of the compressor. Further, the low pressure refrigerant flowing out of the evaporator is separated into gas and liquid by an accumulator and a separated gas-phase refrigerant is sucked from a suction port of the compressor. In this way, the gas injection cycle is constructed.
Further, in the patent document 2, in the heat pump cycle constructing the gas injection cycle, by switching the refrigerant flow passage of the cycle in the heat pump cycle constructing the gas injection cycle, three operation modes of cooling, heating, and dehumidifying-heating are realized.
Specifically, by controlling the amount of heat exchange (the amount of heat absorption and the amount of heat radiation) in the outside heat exchanger for exchanging heat between the outside air and the refrigerant according to the operation mode of the air conditioning device, the respective operation modes are realized.
For example, in the cooling operation, by radiating heat held by the refrigerant to the outside air in the outside heat exchanger, the amount of heat absorption of the refrigerant in the evaporator is secured to thereby cool the blown air to a desired temperature, whereas in the heating operation, by absorbing heat from the outside air in the outside heat exchanger, the amount of heat radiation in the radiator is secured to thereby heat the blown air to a desired temperature.